Oddělení dielektrik ve Fyzikálním ústavu AVČR. Stanislav Kamba
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Transcript Oddělení dielektrik ve Fyzikálním ústavu AVČR. Stanislav Kamba
Asymmetry in Standard model:
(2.300..56 ) x104
Experimentally obtained:
(73.6 26.6) x104
Výzkum a praktické využití magnetických feroelektrik
Stanislav Kamba
Fyzikální ústav AVČR, Na Slovance 2,
182 21 Praha 8 [email protected]
Multiferoika jsou materiály, ve kterých
koexistují dvě a více feroických vlastností.
Ferroelectric
Ferromagnetic
Ferrotoroidic
Ferroelastic
Sketch of MERAM element
Bibes & Barthélémy, Nature Materials, 7, 425 (2008)
Chen et al. APL 89, 202508 (2006)
Tunnel junctions with multiferroic barriers
M || M
M || M
La0.1Bi0.9MnO3 magnetoferroelectrics,
2 nm thin film
M. Gajek et al. Nature Materials, 6, 296 (2007)
Classification of insulating oxides
Béa et al. JPCM 20, 434221(2008)
Fiebig, J. Phys. D: Appl. Phys. 38, R123 (2005)
Multiferroics with spiral magnetic structure
Kimura et al. Nature 426, 55 (2003)
T. Kimura Annu. Rev. Mater. Res. 37, 387 (2007)
TbMnO3, TN=40 K, TC=27 K
Different types of multiferroics
• Type-II: Magnetically driven multiferroics, TC < TN
a)Multiferroics with spiral magnetic structure
P eij ( Si S j )
The inverse Dzyaloshinskii-Moriya mechanism
- constant proportional to the spin orbit coupling and superexchange interaction
eij – unit vector connecting the neighboring i and j sites
b) Multiferroics with collinear magnetic structure
P ( Si S j )
Symmetric (Si.Sj)-type interaction, termed (super)exchange striction
T. Kimura Annu. Rev. Mater. Res. 37, 387 (2007)
H. Kimura et al. J. Phys. Soc. Jpn. 75, 113701 (2006)
Strain induced ferroelectricity and ferromagnetism
in tensile strained EuTiO3/DyScO3
Lee et al. Nature 466, 954 (2010)
FZÚ AVČR; [email protected]
Strain-induced ferroelectric phase transition in EuTiO3/DyScO3
+1% tensile strain
160
1.0
0.9
coupled
TO1 and TO2
phonons
140
SM
0.8
0.6
0.5
0.4
TO2
0.3
0.2
EuTiO3 on DyScO3
0.1
E || [110]
TO4
0.0
100
200
300
400
500
EuTiO3/DyScO3
JHL1323, 100 nm
measured in polarization
E||[110] of DyScO3
-1
Reflection
0.7
120
TO (cm )
T = 10 K
T = 50 K
T = 75 K
T = 100 K
T = 120 K
T = 150 K
T = 180 K
T = 200 K
T = 225 K
T = 250 K
T = 275 K
T = 300 K
TO2
100
80
TO1 soft mode
60
TC
TAF
40
0
50
100
600
150
200
250
300
Temperature (K)
-1
Wavenumber (cm )
1800
0.8
0.7
1600
DyScO3
JHL1323, 100 nm
1400
0.6
E|| (110)
E|| (001)
1200
0.5
0.4
10 K
70 K
120 K
180 K
220 K
250 K
275 K
300 K
0.3
0.2
0.1
0.0
100
200
300
400
-1
Wavenumber(cm )
500
600
'(0)
Reflectivity
EuTiO3/DyScO3
1000
800
(0) phj
PS 30 C/cm2
600
TC
400
200
Nature 476, 114 (2011)
0
0
Lee et al. Nature 466, 954 (2010)
50
100
150
200
Temperature (K)
250
300
Strain induced ferromagnetism in tensile strained EuTiO3/DyScO3
Lee et al. Nature 466, 954 (2010)
Magnetic dependence of TO1 phonon frequency
EuTiO3/ LSAT
0.75
B=0.0 T
B=0.5 T
B=1.0 T
B=1.5 T
B=2.0 T
B=2.5 T
B=3.0 T
B=3.5 T
B=4.0 T
B=5.0 T
B=6.0 T
B=8.0 T
Reflectance
0.70
T= 1.8 K
0.65
0.60
0.55
T = 1.9 K
0.58
EuTiO3/LSAT
Reflection
EuTiO3/LSAT d=42 nm
d=22 nm
0.56
0.0 T
1.0 T
1.5 T
2.0 T
3.0 T
4.0 T
6.0 T
8.0 T
10.0 T
11.0 T
13.0 T
0.54
0.52
0.50
0.45
0.50
90
95
100
105
-1
Wavenumber (cm )
110
115
95
100
8
105
110
-1
Wavenumber (cm )
7
42 nm; T= 1.8 K
22 nm; T= 4.2 K
22 nm; T= 1.9 K
5
4
TO1 (cm-1)
'(B)/'(0) (%)
EuTiO3/LSAT
105
6
115
104
3
1.9 K (22 nm)
4.2 K (22 nm)
1.8 K (42 nm)
103
2
1
102
0
0
2
4
6
B (T)
8
10
12
14
0
Kamba et al. PRB 85, 094435 (2012)
2
4
B (T)
6
8
Comples THz spectra of YMnO3
single crystal
H
E
Kadlec et al. PRB 84, 174120 (2011)
n* * *
H
k
E
k
Predictions for the EDM magnitude of electrone
Electron with an electric dipole moment
• d = a s; switching the electric dipole moment
switches the spin moment
+
-
switch s with H
or
switch d with E
+
• Material property requirements:
–
–
–
–
Ferroelectric, switchable at few K, large polarization
Magnetic, but not ordered at a few K
Macroscopic sample (around 1 cm)
A low temperature multiferroic!
K.Z. Rushchanskii et al., Nature Materials, 9, 649(2010)
EuTiO3
TN=7 K
paraelectric
a=3.9 Å
(Eu,Ba)TiO3
BaTiO3
ferroelectric
a=4.0 Å
Dielectric and magnetic properties of Eu0.5Ba0.5TiO3
Orthorhombic Amm2 Cubic Pm3m
2
P (C/cm )
45000
TN=1.9 K
1 Hz
TC=215 K
T
135 K 8
32 K
4
9K
'
-4
-8
15000
0.06
10
20
E (kV/cm)
70
0.05 0 Oe
f = 50 Hz
1 MHz
0
80
1 Hz
Eu0.5Ba0.5TiO3
M (emu/g)
-10
(emu/(g Oe))
30000
0.04
0.03 1000 Oe
50
1.7 K
1.9 K
5.0 K
40
30
20
Eu0.5Ba0.5TiO3
10
0.02 3000
0
0.2
0.01 5000 Oe
tan
60
0
1
2
4
3
4
5
H (10 Oe)
0.00
0.1
0
1 MHz
0.0
0
50
100
150
200
Temperature (K)
250
300
2
4
6
8
10
Temperature (K)
Rushchankii et al., Nature Materials, 9, 649 (2010)
V. Goian et al. JPCM 23, 025904 (2011)
S. Kamba, Čs. čas. fyz. 60, 329 (2010)
Elekromagnetické spektrum
„THz
OPTIKA
mezera”
nízké
radiové mikroviditelné rtg. gamma
Infrač.
UV záření
frekvence vlny
vlny
ELEKTRONIKA
100
103
kilo
106
mega
1000 km 1 km
109
giga
1012
tera
1 m 1 mm
1015
peta
1018
exa
1021 1024
zetta yotta
1 μm 1 nm 1 pm 1 fm
frekvence
[Hz]
vlnová
délka
„tradiční“ zdroje – příliš slabé:
Při frekvencích > 10 GHz
klesá účinnost obvodů:
elektrony nestačí sledovat
rychlé změny elmg. pole
Při frekvencích < 10 THz
optické zdroje září málo
FZÚ AVČR; [email protected]
I.3. Dielectric spectrum
* ' i "
* * , T
A set of the frequency temperature dependences
should be studied
'
LF
IR
RF
3
6
10
10
OPT
9
12
10
10
Frequency, Hz
1
15
10
18
10
Dielectric spectrum – a sum of the dielectric dispersion regions
j 2j
n
* ( )
j 1
i j
2
j
2
m
j 1
Rj
1 it Rj
FZÚ AVČR; [email protected]
THz laboratoř
FZÚ AVČR; [email protected]
Magnetický kryostat v THz laboratoři
FZÚ AVČR; [email protected]
Infračervená laboratoř
FZÚ AVČR; [email protected]